Here on the Michigan UP's Keweenaw Peninsula, we are a solid zone 5, despite the fact that if you look at the zone map we are squarely in the middle of what is otherwise a zone 3 (with a little border of zone 4 on the southern edge of Lake Superior). The reason we're a zone 5 is that we have a more temperate climate due to the lake effect. We're a little cooler in the summer, but warmer in the winter and also typically have a very heavy snow cover that allows for zone 5 (and sometimes even higher zone) plants to survive and even thrive.

But, we do have very short summers, with long somewhat cool days. And this makes gardening a whole lot different then it was in the Nebraska zone 5 area where I grew up.

2012 will be my 5th summer in this area. Our flower gardens thrive! My husband and I both love ornamental plants and flowers. We have a small yard that we've filled to overflowing with early spring flowers, hosta, lupines, iris, peonies, hollyhocks, roses, and to a lesser degree a wide variety of companion plants. We also have a camp in the woods where we've planted native flowers, plus a ton of the more 'deer-resistant' perennials.

Strawberries do great too!

But veggie gardening is tougher. Every year, we have great looking tomato plants that are just starting to produce when that first frost hits. Same for peppers. Our onions have been small. Our potatoes are small. We haven't had great luck with anything except peas. So, I'm looking for advice on varieties. Some things, it's a little late for just now locating for this year (although typical last frost date is June 1st so maybe it's really not all that late after all). We do have some tomatoes planted, along with peas, radish, cucumbers, zucchini, and cabbage. But we might still plant other varieties. And there are a lot of things we haven't planted yet.

I'm looking for varieties that will do well and produce well in long cool days and a short season. We like all kinds of veggies, so don't be hesitant to mention things that I didn't list above. What are your best varieties?

And thanks to everyone who makes suggestions!

You might try some of the short season varieties of corn if you want a bit of a challenge. Many are early maturing, short season hybrids. Seed available in many Canadian seed catalogues.

If it is worth mentioning, cherry tomatoes grow like crazy up here. Less time to mature and they are super sweet. I have many but a few favorites. Easily started from seed in April. :)

Ginny

Ginny, I'd noticed other summers that the cherry tomatoes did seem to do better then the other types. I do know there are early tomato varieties. 'Early Girl' comes to mind, but I've never cared for that particular variety. Maybe other early tomatoes are better.

As for onions, assuming you can start your own seedlings (I start them under lights at end of Feb/early March), then Talon is the variety I swear by (long storage, we ate the last of the 2011 crop in late April this year and they were still in pretty good condition). If that won't work for you, then Norland is even earlier, though by March or April it isn't storing so well...
Here's some Talon onions I grew (the coin in the pic is the Cdn $2 coin, a bit over an inch in diameter):

Have you considered rigging up a hoophouse with greenhouse plastic? If your main problem is DAYTIME temperatures being too cool, a hoophouse will work wonders for bringing your warm season crops to maturity. I assume that because of the lake, your nights are relatively warm (50-55?), which the hoophouse will bump up by a couple of degrees as well.

Other veggies that people have mentioned are also great for your climate - beets, chard, any brassica (use row cover to keep pests off), spinach, potatoes, peas, beans.

IME, tomatoes are most fussy about where they grow and how they are cared for in a cool, short season climate. They are built for comfort. :)

Ginny